Differential thermal analysis
The differential thermal analysis ( DTA ) is a thermal method for material analysis . It belongs to the group of methods of thermal analysis . The DTA uses the fact of a characteristic energy turnover at the phase transition for qualitative and quantitative analysis . The measurement is based on a comparison of the temperatures of the sample and a selected reference substance in a symmetrical measuring chamber. The reference substance has no phase transitions in the temperature range to be examined. With a constant supply of energy (heat) through the furnace, the temperature under both crucibles (sample and reference) is measured using temperature sensors and the difference is recorded. Such a temperature difference only appears at phase transitions, and conclusions can be drawn about the composition of the sample from the curve.
Frequent areas of application of the DTA are the investigation of mineral substances, such as the dewatering of clays and the clinker phase formation in cement raw meal, the recording of the heat of reaction during the combustion of organic substances and the characterization of plastics .
Differential thermal analysis is a frequently used method to investigate polymorphism , which is of particular importance in pharmacy for the characterization of some medicinal substances . The DTA allows this complex phenomenon to be recognized and interpreted, especially if the analysis sample is a mixture of several crystal modifications.
In 1975 Bruno Sternad analyzed ski waxes for ski racers at the University of Linz using DTA to determine the melting points and proportions of their mixture components.
A further developed from the DTA method is the differential scanning calorimetry ( English differential scanning calorimetry , DSC). While in the DTA the temperature difference between the two crucibles (sample and reference) is recorded directly as a function of the supplied energy or the temperature of the reference substance, in the DSC the heat flow difference is recorded from this . Characteristic temperatures and caloric parameters can thus be determined.
literature
- DIN 53765, DIN 51007, ASTM E 474, ASTM D 3418
- WF Hemminger, HK Cammenga: Methods of thermal analysis Springer-Verlag, ISBN 3-540-15049-8 , ISBN 0-387-15049-8
Individual evidence
- ^ Herbert Feltkamp, Peter Fuchs, Heinz Sucker (editors): Pharmaceutical Quality Control , Georg Thieme Verlag, 1983, pp. 307-319, ISBN 3-13-611501-5 .